1. Field of the Invention
The present invention relates to a hydrodynamic bearing device used in a spindle motor or the like, and to a spindle motor and a recording and reproducing apparatus.
2. Description of the Related Art
Hydrodynamic bearing devices (hereinafter referred to as hydrodynamic bearings) that afford lower NRRO (non-repeatable runout) and are quieter because of non-contact rotation have been used in recent years in the spindle motors installed in hard disk drives (hereinafter referred to as HDDs) and other such disk driving apparatus. A hydrodynamic bearing has a structure in which a fluid (hereinafter referred to as a lubricating fluid) fills a gap between a stationary portion and a rotary portion, and to attain precise operation, it is essential to prevent leakage, etc., of the lubricating fluid, and to accurately manage the fill state of the lubricating fluid.
In general, a sealed structure is provided at the open end of the hydrodynamic bearing to prevent leakage of the lubricating fluid from the open end. One such sealed structure has a taper provided on the axial direction upper side, etc., of the rotary portion, so that the shape of the gap between the stationary portion and the rotary portion is tapered, increasing in size outward from the center of the rotational axis. This not only prevents leakage of the lubricating fluid by utilizing the surface tension of the lubricating fluid, but is also effective in terms of filling the gap with the lubricating fluid by utilizing capillary action when the lubricating fluid is poured in.
One method for managing the amount of lubricating fluid added is to measure the height of the lubricating fluid level using a measuring apparatus that combines an auto-focus microscope and a magnetic scale or the like (Patent Document 1: Japanese Laid-Open Patent Application 2001-90733). Another method is to provide an interface deformation portion so that the level of the lubricating fluid can be checked by eye to see if it is at the specified value (Patent Document 2: Japanese Laid-Open Patent Application 2007-182946).